1. Technical Field
The present invention relates to a thermal detector, a thermal detection device and electronic instrument, and to a method for manufacturing the same.
2. Related Art
Known thermal detection devices include pyroelectric or bolometer-type infrared detection devices. An infrared detection device detects infrared rays by creating an electromotive force in a detection element (pyroelectric-type) or varying a resistance value (bolometer-type) on the basis of heat evolved by infrared absorption in an infrared-absorbing film.
In order to increase the infrared absorption to enhance sensitivity, a technique has been proposed in which a diaphragm on which an infrared-absorbing film is formed is supported on a substrate via a cavity, and the distance between the infrared-absorbing film and a total reflection film formed on the substrate so as to face the cavity is set to λ/4n (λ: infrared wavelength; n: an integer) (Japanese Laid-Open Patent Publication No. 2000-205944 (FIGS. 2 and 3)).
A structure in which a plurality of upper infrared-absorbing layers is arranged at intervals from each other on a lower infrared-absorbing layer, and reflecting films are formed on each of the upper and lower infrared-absorbing layers has also been proposed for increasing infrared absorption to enhance sensitivity (Japanese Laid-Open Patent Publication No. 2003-304005 (FIG. 2)).
A technique has also been proposed in which a first infrared-absorbing film is formed on the lateral surfaces of a V-shaped concave portion, a second infrared-absorbing film is formed on the bottom surface of the V-shaped concave portion, and infrared rays reflected by one of the first and second infrared-absorbing films are directed to the other infrared-absorbing film in order to reduce loss due to reflection on the infrared films and increase detection sensitivity (Japanese Laid-Open Patent Publication No. 7-190854 (FIG. 2)). In Japanese Laid-Open Patent Publication No. 7-190854, absorption efficiency is increased by setting the tilt angle of the V-shaped concave portion so that a total of three reflections occur at the first and second infrared-absorbing films, so as to increase the number of incidences on the infrared-absorbing films.